import com.fasterxml.jackson.databind.ObjectMapper;
import com.mysql.jdbc.jdbc2.optional.MysqlDataSource;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sql.DataSource;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

class Message {
    public String from;

    public String to;
    public String message;

    @Override
    public String toString() {
        return "Message{" +
                "from='" + from + '\'' +
                ", to='" + to + '\'' +
                ", message='" + message + '\'' +
                '}';
    }
}

@WebServlet("/message")
public class MessageServlet extends HttpServlet {
    private ObjectMapper objectMapper = new ObjectMapper();

    DataSource dataSource = new MysqlDataSource();
    public void init() {
        ((MysqlDataSource)dataSource).setUrl("jdbc:mysql://127.0.0.1:3306/messageWall?characterEncoding:utf8&useSSL=false");
        ((MysqlDataSource)dataSource).setUser("root");
        ((MysqlDataSource)dataSource).setPassword("1234");
    }

    //1.建立数据源

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Message message = objectMapper.readValue(req.getInputStream(),Message.class);
        System.out.println(message);

//        messageList.add(message);
        //保存数据
        try {
            save(message);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
        resp.setStatus(200);
        resp.getWriter().write("ok");
    }

    private void save(Message message) throws SQLException {
        //1.建立连接
        Connection connection = dataSource.getConnection();
        //2.构造sql
        String sql = "insert into message values(?,?,?)";
        PreparedStatement statement = connection.prepareStatement(sql);
        statement.setString(1,message.from);
        statement.setString(2,message.to);
        statement.setString(3,message.message);
        //3.执行mysql
        statement.executeUpdate();
        //4.回收资源
        statement.close();
        connection.close();
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setStatus(200);
        resp.setContentType("application/json;charset=utf8");
        List<Message> messageList = null;
        try {
            messageList = load();
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
        String respJson = objectMapper.writeValueAsString(messageList);
        resp.getWriter().write(respJson);
    }

    private List<Message> load() throws SQLException {
        //1.建立连接
        Connection connection = dataSource.getConnection();
        //2.构造mysql
        String sql = "select * from message";
        PreparedStatement statement = connection.prepareStatement(sql);
        //3.执行mysql
        ResultSet resultSet = statement.executeQuery();
        //4.遍历集合
        List<Message> list = new ArrayList<>();
        while(resultSet.next()) {
            Message message = new Message();
            message.from = resultSet.getString("from");
            message.to = resultSet.getString("to");
            message.message = resultSet.getString("message");
            list.add(message);
        }
        //5.回收资源
        resultSet.close();
        statement.close();
        connection.close();
        return list;
    }
}

